1. Field of the Invention
The present invention relates to a positioning device and position method.
2. Description of the Related Art
A positioning device having an autonomous navigation function has been known. According to the autonomous navigation function, after positioning of a reference point is performed by using a positioning unit which can measure an absolute position such as GPS (Global Positioning System) or the like, for example, a moving direction and a moving amount are measured by autonomous navigation sensor such as an acceleration sensor, an azimuth sensor, etc., and displacement data obtained by the autonomous navigation sensors is successively accumulated into the position data of the reference point, thereby calculating the position data of each point on a moving route.
Some correcting techniques have been hitherto proposed for the positioning device having the autonomous navigation function. According to these correcting techniques, when calculation of position data based on the autonomous navigation function and positioning based on GPS are simultaneously performed at some point, the position data of that point is corrected on the basis of a positioning result and also a measurement error of the autonomous navigation sensor is corrected on the basis of a positioning result of GPS (for example, JP-A-2008-232771, JP-A-11-230772).
The positioning devices of the related arts have a problem that it would be impossible to calculate position data of each point during movement if position data of a starting point is separately obtained by some means when the positioning based on the autonomous navigation function is performed in the positioning device.
The position data obtained by the positioning device is not only used on a real-time basis during movement, but also used to check past movement points after the movement. Accordingly, even when position data is not obtained on a real-time basis, it may be required afterwards to obtain position data of each point which has been passed in the past.